1. Field of the Invention
The present invention relates in general to a burner control system, and more particularly to a system and a method for controlling a blower motor and an electronic pump of a burner.
2. Background of the Invention
The conventional oil burner is provided with a blower motor adapted to draw air and supply it to a burner and with an electronic pump adapted to draw oil from an oil tank and supply it to the burner. Both the blower motor and the electronic pump should supply the optimum amount of air and oil to the burner in accordance with the combustion conditions of the burner in order to stabilize combustion and to minimize the occurrence of an oil odor developing thereby maximizing the combustion efficiency of the burner.
An apparatus for controlling such a burner is disclosed in U.S. Pat. No. 4,243,372. This patent utilizes a burner control apparatus for use with a fuel burner installation that has an operating control to produce a request for burner operation, a flame sensor to produce a signal when a flame is present in the monitored combustion chamber, and one or more devices for the control of ignition and/or fuel flow. The burner control apparatus comprises a lockout apparatus for de-energizing the burner control apparatus, a control device for actuating the ignition and/or fuel control devices, and a timing circuit that provides four successive and partially overlapping timing intervals of precise relation, including a purge timing interval, a pilot ignition interval, a pilot stabilization interval and a main fuel ignition interval. A burner control system is also disclosed which verifies proper operation of certain sensors in the burner or furnace, including particularly, an air flow sensor which prevents an attempt to ignite the burner if a condition is detected which indicates that the air flow sensor has been bypassed or wedged in the actuated position.
The burner control apparatus of U.S. Pat. No. 4,243,372 includes a first and a second timing circuits, a lockout relay, and a flame sensor failure detecting circuit, for the purpose of detection of malfunction of sensors, i.e., flame sensor failure, air flow sensor failure during purge, pilot flame sensor failure and loss of air flow during combustion, thereby enabling operations of a blower, a burner motor, a main fuel supply and a pilot fuel supply to be controlled.
Also taught in U.S. Pat. No. 4,243,372 is a safety device for protecting the user from fatal injuries which could result from the burner and peripheral devices. However, there is no teaching regarding any method of individually controlling the blower motor and the electronic pump based on quantity of heat generated from the burner. In other words, U.S. Pat. No. 4,243,372 does not teach developing the optimum/maximum quantity of heat from the burner by means of the blower motor and the electronic pump.
Japanese Laid-open Patent No. Sho 59-142330 teaches an improvement in improper combustion in a burner by varying the rotation of the blower motor with reference to a variation in voltage. A burner control apparatus is disclosed for use with a forced combustion burner installation that provides a reasonable quantity of air in connection with the quantity of gas supplied. The apparatus comprising an integrating circuit for detecting a positive half-wave peak value of a source voltage being applied to a combustion air supply motor, a switching device for discharging the integrating circuit by negative half-wave, an analog/digital converter for converting the peak value of the source voltage into a digital value, a timing synchronizer for transferring the digital value from the analog/digital converter to a microcomputer containing an arithmetic section therein, and a phase controller for receiving output from the arithmetic section, the arithmetic section having a correction operating function.
Japanese Laid-open Utility Model No. Sho 52-2335, discloses a burner control apparatus which sequentially controls the supply of fuel to the burner in multi-steps in accordance with the detected quantity of heat. The burner control apparatus comprises a return nozzle for receiving fuel oil from a fuel supply source at a constant pressure. The return nozzle includes a return section for returning part of the supplied fuel oil to the fuel supply source, an electronic valve disposed at the return section of the return nozzle, a temperature-sensitive device for sensing the temperature of a load, and a multi-single thermostat consisting of a plurality of electronic thermostat circuits with each circuit actuated in sequence in response to the operation of the temperature sensitive device. Thus, the combustion of the burner is controlled sequentially in multi-steps in accordance with the operation of the thermostat. The above techniques are designed for the purpose of increasing the combustion efficiency of the burner.
FIG. 1 illustrates a circuit diagram of a typical burner control apparatus which controls the blower motor and the electronic pump of the burner in accordance with the prior art. As illustrated, the burner control arrangement includes terminals A and B adapted to be connected to a suitable source of power. In a high combustion mode (high heat output), the contact "C" of the relay 3 for the blower motor 1 is switched to a high position "a" and the contact "C" of the relay 4 for the electronic pump 2 is switched to a drive position "a", while the contact "C" of the relay 5 is switched to an open position "b", so that voltage across the terminals A and B is applied via the high terminal "a" of the relay 3 to a condenser 10 and a resistor 11 and also to the blower motor 1 and via the drive terminal "a" of the relay 4 to the electronic pump 2. As a result, the blower motor 1 and the electronic pump 2 are driven in a high output condition, resulting in the high burner combustion, i.e. high heat output.
In the medium-output (medium range heat output) combustion mode, the contact C of relay 3 in the blower motor 1 is switched to a low position "b"; the contact "C" of relay 4 for the electronic pump 2 is switched to the drive position "a", contact "C" of a relay 6 is switched to a contact position "b" bypassing variable resistor 14, and the contact "C" of relay 5 is switched to a closed position "a". As a result, the voltage across the terminals A and B is applied via the low terminal "b" of the relay 3 to a condenser 12 and a resistor 13 and also to the blower motor 1 and via the drive terminal "a" of relay 4 and the closed terminal "a" of relay 5 to the electronic pump 2, so that the output of the blower motor 1 and the electronic pump 2 is at a midlevel condition.
In the low output (low heat output) combustion mode, the contacts "C" of relays 3 through 5 are switched to the same contact positions as those in the mid-output combustion mode, except that the contact "C" of relay 6 is switched to a contact position "a" via the variable resistor 14. Thus, the voltage varied by the variable resistor 14 is applied to the electronic pump 2, resulting in the electronic pump 2 being driven in a low output condition.
As described above, the conventional burner control arrangement performs the selection of heat output only at three stages, i.e., high, medium and low, so as to determine quantity of oil supplied to the burner.
Also, as mentioned above, the contacts of relay 3, which are connected to taps disposed at coils of the blower motor, are selected to determine the output of the blower motor 1.
Therefore, the number of rotations of the blower motor 1, i.e. output of the blower motor, is selected in accordance with the voltage induced from the taps of the motor 1, and the frequency of an electronic pump control circuit is varied by changing the contact of the relays connected to the electronic pump 2, so that the quantity of oil being supplied to the burner can be varied.
As described above, the speed of the blower motor and the quantity of oil delivered by the electronic pump are selected to yield a high, a medium or low output, in accordance with the selection of heat desired to be generated. Thus, the number of rotations of the blower motor and the quantity of discharge from the electronic pump are fixed notwithstanding the combustion conditions of the burner.
However, the conventional burner control arrangement as described above has the disadvantage, in that the operations of the blower motor and electronic pump in the initial combustion state are not in agreement with the actual combustion conditions of the burner. This results in unstable combustion which in turn results in an intense oil odor and decreased combustion efficiency of the burner.
Also, the conventional burner control arrangement has additional defects in that when the amount of fuel is controlled in accordance with amount of heat being generated from the burner during operation of the burner, the speed of the blower motor is not controlled, and when the speed of the blower motor is controlled based on a variation in voltage, the amount of fuel being supplied to the burner is not controlled.